Currently employed medical imaging diagnostic apparatuses include CT (Computed Tomography) scanners, MRI (Magnetic Resonance Imaging) apparatuses, PET (Positron Emission Tomography) apparatuses, angiography apparatuses, MRA (MR Angiography) apparatuses and the like. For obtaining CT images of a patient with the abovementioned apparatuses, a chemical liquid such as a contrast medium or physiological saline is often injected into the patient's body.
In general, the injection of the chemical liquid into the patient is automatically performed by using a chemical liquid injector. The chemical liquid injector has an injection head on which a syringe filled with the chemical liquid is removably mounted and an injection control unit which controls the operation of the injection head. The syringe has a cylinder and a piston inserted thereinto to be movable in its axis direction. The chemical liquid is filled in the cylinder. The injection head includes a piston driving mechanism for pushing the piston of the syringe mounted on the injection head into the cylinder. After an injection needle is connected to the end of the cylinder through an extension tube and is inserted into a patient's blood vessel, the piston driving mechanism pushes the piston into the cylinder, so that the chemical liquid in the cylinder can be injected into the patient.
To inject the chemical liquid in the syringe reliably and safely in the abovementioned chemical liquid injector, it is important to allow the injection head to hold the syringe tightly. Patent Document 1 has disclosed a chemical liquid injector in which a pair of holding members is provided for holding a cylinder flange provided integrally with a cylinder of a syringe from both sides of the syringe on the left and right such that the holding member is held at a closed position for holding the syringe or at an opened position for allowing the insertion of the syringe depending on the mounting or demounting operation of the syringe.
There are a plurality of types of syringes having different diameters. For mounting a syringe having a smaller diameter than a standard diameter of a syringe mounted on the injection head, the syringe having the smaller diameter is mounted on the injection head with an adapter interposed between them. The adapter is typically formed to be mounted removably on the injection head and has an adapter body formed in semicylindrical shape for placing the syringe having a small diameter. The adapter body has an integrally formed flange portion at a trailing end for holding by a holding member of the injection head. The cylinder flange of the syringe is provided to be held in a groove formed in the flange portion. The adapter also has a mechanism for fixing the syringe.